This invention relates to a hood assembly for use with a display to reduce unwanted light reflected from a surface of the display. The display may be, for example, a VDU screen, a traffic light or a viewing window, but other applications are described later.
When a VDU screen is viewed under conditions of high ambient light, such as when a television monitor is used for an outside broadcast, or when sun shines on the VDU screen of a bank-note dispensing machine, the ambient light reflected from the screen can make it extremely difficult for the user to discern the image displayed on the screen.
Also, VDU screens used in normal office lighting conditions can cause eye strain.
Although various filter devices are available for mounting over VDU screens, they are not generally found to alleviate the problem to any significant degree, despite their substantial cost in many cases.
We are aware that hood assemblies for cathode ray tube devices were disclosed in patent specifications no. GB 898770 and 930848 of Decca. Such hood assemblies incorporated an inclined filter. The filter of GB 930848 is described as `a neutral filter or a tinted filter` but the filter characteristics are not described. The filter of GB 898770 is a circularly-polarising filter.
Although the hood assemblies of those specifications were described as being suitable for use with television receivers such devices are not commercially available despite the widely-acknowledged problem of eye-strain caused by viewing VDU displays for long periods.
The use of a clear polycarbonate filter in a hood assembly has also been proposed in specification GB 2238937A published as recently as 1991.
I have discovered quite unexpectedly that a hood assembly incorporating a partially reflecting mirror having a relatively low light transmittance provides greatly increased visibility of a VDU display in high ambient light conditions, despite the fact that a low light transmittance mirror would be expected to reduce the overall amount of light reaching the user's eye from the VDU display. In practice the perceived contrast of the display is increased.